Megadrive 1 power regulators

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Lardo Boffin
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Megadrive 1 power regulators

Post by Lardo Boffin » Thu Oct 12, 2017 10:43 am

Hi all

I have decided to recap my early Megadrive in a bid to reduce the vertical lines on the screen (‘jail bars’) as this is the first bit of advice offered on the web.
Aside from finding around 30 electrolytic capacitors and a Z80(!) and have found a couple of 7805 regs connected to a heatsink:-
DDBE933B-D10D-40DB-8320-0A3C7A3AB549.jpeg
Is there a modern version of these I can use and get rid of the heat sink?

Thanks

Lardo
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Re: Megadrive 1 power regulators

Post by 1024MAK » Thu Oct 12, 2017 11:06 am

I think you know the answer... [-X

Either use a RECOM or a TRACO type like in the links below, they can be used to replace 7805 voltage regulators in most applications :wink: .

Prices on these DC/DC converters/regulators often change, so also check the prices of other suppliers ;)

Here are some part numbers and links:-
Recom R-785.0-1.0
https://www.rapidonline.com/recom-r-785 ... er-84-2573
http://uk.farnell.com/recom-power/r-785 ... dp/1793143

Traco Power TSR 1-2450
https://www.rapidonline.com/tracopower- ... 1w-51-7072
http://uk.farnell.com/tracopower/tsr-1- ... dp/1696320

Oh, and even the Wikipedia page says it has a Z80 in it!

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Re: Megadrive 1 power regulators

Post by vanpeebles » Thu Oct 12, 2017 11:52 am

I'm a Megadrive fanboy, and the Z80 does the sound :)

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Re: Megadrive 1 power regulators

Post by Lardo Boffin » Thu Oct 12, 2017 12:01 pm

1024MAK wrote:I think you know the answer... [-X

Mark
Thanks. I have tried to get out of the habit of assuming... I generally seem to get it wrong! :oops:

I did think I had read somewhere about the Z80 but then assumed I had imagined it. Sleep deprivation does weird things to the brain. :?
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Re: Megadrive 1 power regulators

Post by 1024MAK » Thu Oct 12, 2017 12:42 pm

Lardo Boffin wrote:
1024MAK wrote:I think you know the answer... [-X

Mark
Thanks. I have tried to get out of the habit of assuming... I generally seem to get it wrong! :oops:

I did think I had read somewhere about the Z80 but then assumed I had imagined it. Sleep deprivation does weird things to the brain. :?
Just check that the existing 7805 regulator outputs are NOT connected together (directly or via low value resistors). As there are various ways that series type voltage regulator(s) can be used with additional components to produce a higher current (or higher voltage) regulated supply...

Mark

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Re: Megadrive 1 power regulators

Post by danielj » Thu Oct 12, 2017 1:05 pm

The Z80 also allows it to play master system games :) - the powerbase converter was just a straight through more or less:

https://www.youtube.com/watch?v=HIVNTeWKRvw

d.

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Re: Megadrive 1 power regulators

Post by Lardo Boffin » Thu Oct 12, 2017 9:55 pm

Having (finally) removed the heat sink...

No obvious linkage from above:-
0C76AB10-740F-4EAC-9837-99CCFAD18553.jpeg

But from underneath? I can see they have common paths joined by capactitors but not sure if that counts?
3DFB2011-DD85-4F84-9DDF-53B3AB25AB80.jpeg
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Re: Megadrive 1 power regulators

Post by 1024MAK » Fri Oct 13, 2017 12:00 am

It's not really a surprise that the input terminals are linked, or that the 0V/common/ground terminals are linked.

If you use a multimeter on resistance, test between the output terminals, one lead on each output leg. If the result is more than say 500 ohms, they are not linked :wink:

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Re: Megadrive 1 power regulators

Post by vanpeebles » Mon Oct 16, 2017 8:59 am

While it is in bits, you might as well wire up a 50/60hz switch and a region switch too :)

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Re: Megadrive 1 power regulators

Post by trixster » Mon Oct 16, 2017 9:06 pm

That's a good idea. Have you ever heard PAL Sonic and then immediately listened to NTSC Sonic straight afterwards?!? :mrgreen:

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Re: Megadrive 1 power regulators

Post by Lardo Boffin » Mon Oct 16, 2017 9:35 pm

vanpeebles wrote:While it is in bits, you might as well wire up a 50/60hz switch and a region switch too :)
Interesting idea. Are there any recommended web links on how to do this? A quick look up suggests loads and narrowing it down could take a while...
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Re: Megadrive 1 power regulators

Post by vanpeebles » Tue Oct 17, 2017 8:12 am

I'm not too sure, both of mine where already done when I got them, they have metal toggle switches on the back :)


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Re: Megadrive 1 power regulators

Post by Lardo Boffin » Thu May 30, 2019 2:04 pm

After only a brief pause being distracted by other stuff I happened across another cheap issue one Megadrive and so decided to watch some videos (about replacing the 7805) and then decided to ignore the common advice not to do it (as it can introduce noise in the picture and sound output). Some guy in europe somewhere did it without issue so that was good enough for me!

Anyway I ordered two regulators from here:-

https://www.retroleum.co.uk/spectrum-128-modifications

They arrived yesterday and I fitted them today.

The results:-

Stone cold (working) megadrive
No video distortion
No audio distortion

The picture is taken using RF out as I have still not found a cure for the jailbars using the SCART.
B131AC61-D19F-458F-B041-4BDE25D7FA77.jpeg

8)
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Re: Megadrive 1 power regulators

Post by Lardo Boffin » Thu May 30, 2019 2:04 pm

Next up maybe the region mod. :D
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Re: Megadrive 1 power regulators

Post by topcat96 » Thu May 30, 2019 3:15 pm

Jailbar removal mod for MD version 1 mainboards when using RGB socket ...

https://www.youtube.com/watch?v=F5jsUZkI-js
Last edited by topcat96 on Thu May 30, 2019 3:19 pm, edited 2 times in total.
Image

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Re: Megadrive 1 power regulators

Post by Lardo Boffin » Thu May 30, 2019 3:47 pm

Thanks for the link. This kills the composite and svideo out - noob question alert! Does this mean that the console will only work if the TV specifically has an RGB SCART socket, as opposed to a non-RGB SCART socket (i.e. some older / cheaper tellies)?
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Re: Megadrive 1 power regulators

Post by topcat96 » Thu May 30, 2019 3:51 pm

You can fit a switch between the raised pin and the mainboard to re-enable the RF and composite so you can use the console on older tv's however, it will also re-introduce the jailbars.

Dammed if you do and dammed if you don't it seems ...
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Re: Megadrive 1 power regulators

Post by Lardo Boffin » Thu May 30, 2019 7:23 pm

I might do that eventually but I guess if a tv is old enough to have a non-RGB SCART it will probably have a reasonable RF tuner and output from RF is pretty good.
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Re: Megadrive 1 power regulators

Post by CMcDougall » Thu May 30, 2019 8:11 pm

i still have mine, pics in the Other Vintage : viewtopic.php?f=45&t=9401&p=109095&hili ... ve#p109095

& now works again!!

also bought one of these for £20 from Argos :
md.png
it goes to scart with the adaptor for 2 phone leads, also plays your old carts too!
bonus is the wireless controllers for the kids :D
ImageImageImage

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Re: Megadrive 1 power regulators

Post by Lardo Boffin » Thu May 30, 2019 8:43 pm

I know what you are saying about the wireless controllers!

Looks good. I may have to get one when they are on sale next. :D
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Re: Megadrive 1 power regulators

Post by Lardo Boffin » Sun Jun 02, 2019 8:52 am

Before lifting video encoder pins I decided to try a high quality RGB SCART with csync. I got one from retroComputerShack (https://www.ebay.co.uk/itm/Sega-Mega-Dr ... %7Ciid%3A1) and it has improved it to the point where I no longer feel the need to make any more changes.

Before:-
19C24E8B-6FEC-4D65-9CA9-0DA4E0DBB220.jpeg
After:-
D8D145E8-C0AA-4510-96F5-08F4030F6678.jpeg

They are still there just about but no longer visible from a reasonable playing distance from the screen. The ‘before’ actually looks worse than in the photo - my phone camera doesn’t really capture how bad it is in the dark blue area.

£13 well spent. :D
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Re: Megadrive 1 power regulators

Post by chinnyhill10 » Fri Jun 07, 2019 8:35 pm

vanpeebles wrote:
Mon Oct 16, 2017 8:59 am
While it is in bits, you might as well wire up a 50/60hz switch and a region switch too :)
So easy even I have done it. On the original they may as well have put a big label on the links to say "mod here"

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Re: Megadrive 1 power regulators

Post by chinnyhill10 » Fri Jun 07, 2019 8:35 pm

Lardo Boffin wrote:
Sun Jun 02, 2019 8:52 am

£13 well spent. :D
Sorry I didn't see this earlier. C Sync is the answer. You shouldn't need to do anything else.

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Re: Megadrive 1 power regulators

Post by Lardo Boffin » Tue Jun 18, 2019 4:09 pm

chinnyhill10 wrote:
Fri Jun 07, 2019 8:35 pm
vanpeebles wrote:
Mon Oct 16, 2017 8:59 am
While it is in bits, you might as well wire up a 50/60hz switch and a region switch too :)
So easy even I have done it. On the original they may as well have put a big label on the links to say "mod here"
I probably should have found a smaller switch but it does the job. Very easy install. Thanks for the link!

A80E10D2-09A9-4E88-910D-46C6F9701A3E.jpeg
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